Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with atransitional graphical user interface showing a first image in asequence according to a first embodiment of our new design;

FIG. 2 is a front view thereof showing a second image in the sequence;

FIG. 3 is a front view thereof showing a third image in the sequence;

FIG. 4 is a front view thereof showing a fourth image in the sequence;

FIG. 5 is a front view of a display screen or portion thereof with atransitional graphical user interface showing a first image in asequence according to a second embodiment of our new design;

FIG. 6 is a front view thereof showing a second image in the sequence;

FIG. 7 is a front view thereof showing a third image in the sequence;

FIG. 8 is a front view thereof showing a fourth image in the sequence;

FIG. 9 is a front view of a display screen or portion thereof with atransitional graphical user interface showing a first image in asequence according to a third embodiment of our new design;

FIG. 10 is a front view thereof showing a second image in the sequence;

FIG. 11 is a front view thereof showing a third image in the sequence;and,

FIG. 12 is a front view thereof showing a fourth image in the sequence.

The outermost broken line illustrates a display screen or portionthereof and forms no part of the claimed design. The dot-dash brokenlines in the figures illustrate boundaries which form no part of theclaimed design. The remaining broken lines represent elements of thedisplay screen or portion thereof with a transitional graphical userinterface that form no part of the claimed design. The appearance of thetransitional image sequentially transitions between the images shown inFIGS. 1-4 in the first embodiment, FIGS. 5-8 in the second embodiment,and FIGS. 9-12 in the third embodiment. The process or period in whichone image transitions to another image forms no part of the claimeddesign.

CLAIM We claim the ornamental design for a display screen or portionthereof with a transitional graphical user interface, as shown anddescribed.